Dipicolylamino quinoline derivative as novel dual fluorescent detecting system for Hg2+ and Fe3+

Novel quinolinyl oxazolidinonyl dipicolylamine derivatives (QOD) were synthesized via halo-induced cyclization of t-butyl allyl(quinolinyl) carbamate followed by substitution of dipicolylamine (DPA). One of the quinoline derivatives, 6QOD, shows a remarkable fluorescent enhancement in both Hg2+ in aqueous media and Fe3+ in CH3CN over other metal ions with a detection limit of 1.01 and 0.22 mu M, respectively. Moreover, the complexation was proved to be a 1:1 stoichiometric binding by Job's plot and MS data. 6QOD was confirmed to form a bidentate binding with Hg2+ (K-a= 6556M(-1)) and Fe3+ (K-a= 27,700M(-1)) as evidenced by the chemical shifts in H-1 NMR experiments of the DPA protons and the oxazolidinonyl protons in an excellent agreement with the most stable complex structures for both metal ions revealed by the DFT study. Both sensing mechanisms probably involve PET inhibition between the DPA unit and quinoline. The advantage of this 6QOD probe is that it can effectively be applied as a selective Hg2+ and Fe3+ chemosensor by adapting the proper dualsensing system.